Extrusion press for rod or tube

ABSTRACT

A hydraulic rod and tube extrusion press having a main extrusion ram and a piercer connected to a piston which works in a cylinder within the extrusion ram. In order to extrude tube around the piercer with the tip of the piercer stationary in the mouth of the die means are provided for supplying fluid to the return stroke chamber of the piercer piston cylinder so that the piercer is retracted at an appropriate rate relatively to the extrusion ram as the extrusion ram advances.

O United States Patent 1 [111 3,709,013 Petsch [451 Jan. 9, 1973 [54]EXTRUSION PRESS FOR ROD OR [56] References Cited TUBE UNITED STATESPATENTS [75] inventor: Ernst Petsch, Mettmann, Germany 3,362,208 1/1968Murphy ..72/265 X [73] Assignee: Maschinenfabrik Sack Gmbl-I, Dus-2,063,562 12/1936 Sparks ..72/271 X seldorf-Rath, Germany PrimaryExaminer-Charles W. Lanham [22] Filed: May 1970 Assistant Examiner-R. M.Rogers [2]] APPL No: 38,826 Attorney-McGlew and Toren [57] ABSTRACT [30]Foreign Application p i it Data A hydraulic rod and tube extrusion presshaving a main extrusion ram and a piercer connected to a y 29, 1969Germany 19 27 396-2 piston which works in a cylinder within theextrusion ram. In order to extrude tube around the piercer with the tipof the piercer stationary in the mouth of the die [52] US. Cl ..72/22,72/265 means are provided for supplying fluid to the return [5 Intstrokechamber of the piercer piston cylinder so [58] Field of Search ..72/265,22 the piercer is retracted at an appropriate rate relatively to theextrusion ram as the extrusion ram advances.

6 Claims, 6 Drawing Figures PATENTEDJAN 9 I975 3.709013 sum 3 OF 4 INVEN TOR E'RVST PeTsw EXTRUSION PRESS FOR ROD OR TUBE The inventionrelates to hydraulic rod and tube extrusion presses of the kind equippedwith a piercing device consisting of a double-acting hydraulic piercerpiston which supports a piercer and works inside the main extrusion ramof the press.

Extrusion presses of this kind are usually arranged in such a way thattubes can be extruded by either of two alternative methods. By the firstmethod the piercer advances with the main ram during the extrusion ofthe tube. After the piercer has pierced the workpiece blank the ram andthe piercer advance together. By the second method the piercer remainsstationary during the extrusion of the tube. After the piercer haspierced the workpiece blank the piercer continues to advance through ashort distance only and then remains stationary in the mouth of theextrusion die. The piercer then remains stationary in this positionwhile the ram advances, extruding the tube. The first of these twomethods encounters no particular difficulties, but the second method, inwhich the piercer remains stationary during tube extrusion, involves acomparatively costly press construction.

Three methods are known for holding the piercer stationary during tubeextrusion:

By the first method a piercer cylinder containing a rearward extensionof the piercer piston is mounted behind the ram cylinder, the piercerpiston penetrating through the wall of the ram cylinder and through theram piston, and being guided by the hollow ram. At its forward end thepiercer piston supports the piercer holder and piercer. The piercercylinder must be very long to allow for the long total stroke of thepiercer piston. This total stroke includes both the ram piston strokeand the stroke of the piercer piston relative to the ram piston duringwhich the piercer travels all the way from its retracted position in theram punch, through the dummy block and through the workpiece blank intothe mouth of the extrusion die. The long piercer cylinder must bemounted at a distance behind the ram cylinder at least equal to the ramstroke. The entire extrusion press is therefore very long, andcorrespondingly costly to construct.

By the second known method for holding the piercer stationary duringtube extrusion the piercer cylinder containing the piercer piston ismounted to slide in the punch holder through a distance equal to thestroke of the piercer piston relative to the ram. During tube extrusionthe piercer must be held stationary in the mouth of the extrusion die byaxial support. A piercer piston holder has projections which projectoutwards through slots in the punch holder, the movements of theprojections being limited by mechanical stops to agree with the strokeof the piercer relative to the ram. The punch holder must therefore bequite long and the entire extrusion press is correspondingly long. Inparticular this arrangement involves the use of long tension members,which extend undesirably under the influence of the extrusion pressingforces.

By the third method a piercer piston is installed in a rearward andoutward extension of the ram. This method has the disadvantage that theram extension occupies a considerable cross sectional area in the ramcylinder, which must consequently be correspondingly large and costly toconstruct. The extrusion press is rather long, although it is not aslong as the press used in the first of the three methods.

The object of the present invention is to provide for operation of anextrusion press of the kind described which allows the press to beconstructed as short as a conventional press which is suitable only forextruding rod and not suitable for extruding tube.

In accordance with the invention, a method of operating a hydraulic rodand tube extrusion press of the kind equipped with a piercing deviceconsisting of a double acting hydraulic piercer piston which supports apiercer for piercing a workpiece blank and which works inside a mainextrusion ram of the extrusion press, is characterized in that to enabletube to be extruded through a die around the piercer with the piercertip substantially stationary in the mouth of the die, hydraulic fluid isfed into a return cylinder chamber for the piercer piston within themain extrusion ram at a rate of flow such that the piercer is retractedrelatively to the ram and remains substantially stationary whilst themain extrusion ram advances to extrude the tube.

The invention also includes a rod and tube extrusion press for carryingout the method, the press having a piercing device consisting of adouble acting hydraulic piercer piston which supports the piercer forpiercing a workpiece blank and which works inside a cylinder within amain extrusion ram of the extrusion press, there being means which isresponsive to the axial position of the piercer and which controls theflow of hydraulic fluid to a return chamber of the cylinder within themain extrusion ram whereby when the press is set up for extruding tubearound the piercer the piercer can automatically be retracted relativelyto the main extrusion ram so as to maintain the tip of the piercersubstantially stationary within the mouth of the die whilst the mainextrusion ram advances to extrude the tube. With this arrangement, thepiercer is held stationary purely by hydraulic means, and not by anysort of mechanical construction as described above, so that thedisadvantages mentioned are removed.

The invention has the great advantage that it allows a simple pressconstructed exclusively for rod extrusion to be converted easily into apress for rod and tube ex-' trusion merely by replacing the extrusionram, that is to say by installing a different ram, and adding somehydraulic controls, without this involving any increase in the size ofthe machine.

The means responsive to the axial position of the piercer may be amobile trigger, or an electric contact or other control element situatedto one side of the axis of the press and mechanically connected to thepiercer. The control element is mounted on the machine in such a waythat during the operation of the machine the distance between thetrigger and an actuator or other complementary element is always thesame as the distance between the existing position of the piercer andits final, fully advanced position in the mouth of the extrusion die.The actuator actuates a control valve in a hydraulic line which connectsthe piercer cylinder to a source of hydraulic pressure so that when thepiercer has advanced a little beyond its desired forward limitingposition in the mouth of the extrusion die the control valve, actuatedby the trigger through the actuator, admits hydraulic fluid underpressure to the return chamber of the piercer cylinder, thrusting thepiercer piston slightly back again so that thepiercer returns through ashort distance outwards. This is only a very short movement, the piercerremaining essentially in the mouth of the extrusion die. In effect thepiercer is retained constantly, during tube extrusion, at its desiredfinal position in the mouth of the extrusion die, although oscillatingvery slightly about a mean position, from which it deviates. at most bya very few millimeters. This slight oscillating movement of the piercerdoes no harm. Moreover in practice the slight oscillations are ofteneffectively damped by the natural inertia and viscous drag in thesystem.

The mechanical connection between the piercer and the mobile trigger cantake the form of a flexible cable or chain or the like, which is led outthrough the side of the extrusion ram.

In order to allow the press to extrude tube when desired by thetravelling piercer method, in which the piercer advances during theextrusion with the punch, the mobile trigger is preferably arranged sothat it can be rendered inoperative.

An example of a press constructed in accordance with the. invention isshown in the accompanying drawings, in which:

FIGS. 1 to 4 show the press in axial section in a succession ofoperating positions; and,

FIGS. 5 and 6 show, to a larger scale, a hydraulic control valve withauxiliary parts, in two different operating positions.

The extrusion press shown in FIGS. .1 to 4 consists of a ram cylinder 1,a reaction crosshead 2, tie rods 3 with nuts for attaching the ramcylinder 1 to the reaction crosshead 2, a main ram 4, hydraulicconnections 5 and 61on the ram" cylinder 1 for feeding and removing thehydraulic fluid during the forward and return strokes of the ram 4, acontainer 7 and a die holder 8 which is represented diagrammatically andcontains the extrusion die. .On the outer end of the ram 4 there ismounted a punch holder 9 for a punch 10, the reaction thrust from thepunch being taken by a thrust pad 10a.

In FIG. 1 the press is shown before the beginning of the extrusioncycle. A workpiece blank 12 is shown ready for extrusion, a dummy block11,.iwhich has a hole in the middle, being interposed between theworkpiece blank 12 and the ram punch 10.

The ram 4 is hollow and contains a piercer cylinder in which works apiercer piston 13 which drives a piercer 15. The piercer piston 13divides a cylindrical drilling in the interior of the ram4 into twocylinder chambers 13a and 13b. .The piercer piston 13 drives a piercerholder 14 which in turn drives the piercer 15. Hydraulic fluid issupplied to the piercer cylinder 13a, 13b by a simple hydraulic systemconsisting of a pump 16, a tank 17 for hydraulic fluid, and excess fluidrelease valve 18 and a control valve 19 which is actuated, during theoperating of the machine, so as to drive the piercer piston 13 forwardsor backwards, relative to the ram piston 4, or so as to retain thepiercer piston 13 stationary relative to the ram piston 4. This controlvalve 19 is actuated in the known way by means which are not shown inthe drawing. Actuation is usually by electrically controlled solenoidswhich respond to limit switches triggered by the movements of themachine during the operating cycle.

The pressis equipped with a further control valve 20 containing a slider21. A compression spring 22 acts on the slider, tending to hold theslider in the position represented in FIG. 1. The purpose of thiscontrol valve 20, and its method of functioning, will be describedfurther below.

A hydraulic lead 23 connects the pump 16 to the control valve 19 and tothe controlslider valve 20. A

return line 24 takes hydraulic fluid from the valves 19 and 20 back tothe storage tank 17. From the control valves 19 and 20 pressure leads25, constructed in several sections, take hydraulic fluid under pressureto the advance stroke cylinder chamber 13a for advancing the piercerpiston 13 relative to the ram piston 4..

Further hydraulic pressure lines 26, also constructed in severalsections, convey hydraulic fluid under pressure to the return strokechamber 13b for the return stroke of the piercer 15. These two hydrauliclines 25 and 26 are made in articulated sections to allow for themovements of the ram 4 relative to the hydraulic control system.

A cable 27 attached to the piercer piston 13 passes over two deflectorrollers 29, the other end of the cable being coiled on a drum 28 whichis loaded by a spring so as tokeep the cable 27 constantly taut. Thecable 27 passes sideways out of the ram assembly between the two guiderollers 29. Fixed to the cable 27 there is a mobile trigger 30 whichcooperates with an axially adjustable actuator 32mounted on a slidingrod 31 to which there is attached an actuator arm 33 which thrustsagainst the slider 21 of the control valve 20. The slider 21 is theactuating device mentioned further above. The rod 31 slides in a frame34.

The extrusion press functions as follows:

At the beginning of the operating cycle the parts are in the positionsshown in FIG. 1 and the control valve 19 is shut, locking the piercerpiston 13 stationary relatively to the ram 4. If it is desired toextrude a rod from the workpiece blank 12, rather than a tube, thecontrol valve 19 remains closed and the piercer remains housed in thepunch 10. For extruding rod a dummy block 11 without a hole is used. Theprocess of extruding rod need not be described here.

For extruding tube the control valve 19 is actuated to return thepiercer piston 13 into its fully retracted position. A dummy block 11with a hole in the middle is used. The ram 4 is advanced, the ram punch10 driving the workpiece blank 12 into the container 7. The controlvalve 19 is then actuated to drive the piercer 15 forwards by hydraulicpressure applied in the cylinder chamber 131:. The piercer isdrivenforwards through the hole in the dummy block until the piercer strikesthe workpiecev blank 12. The parts are now in the positions shown inFIG. 2. This forward movement of the piercer requires very littledriving pressure in the cylinder chamber 13a. However as soon as thepiercer strikes the workpiece blank 12, hydraulic pressure builds up inthe cylinder chamber 13a. The increasing hydraulic pressure is utilizedto actuate a pressure sensitive switch which returns the control valve19 into its closed position, locking the piercer piston 13 in the ram 4so that the piercer 15 is locked stationary relatively to the presspunch 10. The driving faces of thepunch l0 and of the tip 15a of thepiercer therefore remain stationary relative to each other.

The ram 4 is then driven forwards through a further short distance so asto upset the workpiece blank 12. The parts are now in the positionsshown in FIG. 2. The ram 4 is then retracted through a short distance soas to leave a little space in the container, for receiving the workpiecematerial which will be driven backwards during the piercing operation.To start the piercing operation the control valve 19 is actuated todrive the piercer piston 13 forwards, the ram 4 being lockedhydraulically in position in the ram cylinder 3, so that the ram cannotmove in its cylinder. The piercer advances, piercing the workpiece blank12, until the parts reach the positions shown in FIG. 3. The piercerpiston 13 is now in its forward limiting position, having completed theentire stroke indicated at R in FIG. 3. The parts of the press aredimensioned so that the tip 15a of the piercer is now in the mouth 8a ofthe extrusion die.

Let it be assumed, for the present, that a tube is going to be extrudedby the first method, in which the piercer advances with the punch. Forthis kind of extrusion the valve 19 remains as it is, so that thecylinder chamber 130 behind the piercer piston 13 contains hydraulicfluid under pressure. The mobile trigger 30 is inactivated, so that itcannot cooperate with the actuator 32. The ram 4 advances, the piercer15 advancing with the press punch 10. On the other hand if it is desiredto extrude tube by the second method, the piercer tip 15a must remainstationary in the mouth 8a of the extrusion die during the forwardmovement of the ram 4 and the press punch 10.

The method of functioning of the extrusion press as described up to nowis known. What is new in the present invention is that novel means areused for retaining the piercer tip 15a stationary in the mouth of theextrusion die during extrusion of tube by the second method.

According to the invention, to extrude tube with the piercer tipstationary in the mouth of the die, the control valve 19 is closed, sothat it is inoperative. The mobile trigger 30 is engaged, so that it cancooperate with the actuator 32, that is to say the trigger is broughtback into line with the actuator. All movements of the piercer piston 13relative to the ram 4 are now controlled exclusively by the slider valve20. The further function of the extrusion press will now be describedwith the help of FIGS. 5 and 6.

For tube extrusion with a stationary piercer the mobile trigger 30 isadjusted in position on the cable 27 in such a way that with the piercerpiston fully retracted in the ram, as represented in FIG. 1, thedistance between the trigger 30 and the actuator 32 is equal to thedistance between the piercer tip 150, in the position shown in FIG. 1,and the position of the piercer tip in the mouth ofthe extrusion dieduring tube extrusion, as represented in FIG. 4. During tube extrusionthe forward face of the piercer tip normally projects somewhat into thedie mouth, for example by the amount of the small distance as indicatedin FIG. 3. Under these circumstances the mobile trigger 30 rests incontact with the end face of the actuator 32, as represented in FIG. 5.

A small movement now takes place, both the ram 4 and the piercer 15advancing through a little distance, towards the right in FIG. 4. Thetrigger 30 follows this movement, also advancing through a littledistance towards the right, and so thrusting the actuator 32 and theslider of the valve 20 towards the right. This opens the valve 20,bringing it into the position shown in FIG. 6. Only a small movement ofthe mobile trigger is required to effect this, as indicated at x inFIGS. 5 and 6. With the valve 20 open hydraulic fluid passes from thepump 16 through the lines 23 and 26 into the return cylinder chamber13b, returning the piercer tip 15a through the small distance x, backagain into the position shown in FIG. 5, the valve 20 also opening thehydraulic fluid return line 25, 24 so that hydraulic fluid expelled fromthe cylinder chamber returns to the storage tank 17.

This small movement of the piercer tip 15a can be repeatedintermittently during the extrusion of the workpiece blank 12, thepiercer l5 performing an oscillating movement of amplitude at most equalto x. By suitably constructing the control valve 20 the amplitude ofthis oscillation can be limited to quite a small value, of the order ofa few millimeters. Moreover the natural inertia and viscous drag in thecontrol system usually ensures that the slider of the valve 20 remainsquiescent in an intermediate position such that fluid flows constantlyinto the cylinder chamber'13b and out of the chamber 1311, the piercerremaining practically stationary in the mouth of the extrusion die. Itshould however be observed that an oscillation of the piercer eventhrough the full distance is quite harmless.

For the sake of simplicity in description it has been assumed in thepresent example of the invention that the control device which controlsthe flow of hydraulic fluid is a valve actuated by a mechanical trigger.It would however be perfectly possible to replace the mechanical triggerby an electric contact, the other contact being the actuating device.When the contacts close this actuates the valve electromagnetically.This arrangement would shorten the distance x. As a further alternativeinstead of using a control valve a variable delivery pump could be usedas the pump 16, for controlling the supply of hydraulic fluid to returnthe piercer tip. The variable delivery pump could be controlledmechanically or electrically. If electric control is used the mechanicaltrigger 30 can be replaced by an electric sliding contact which slideson a potentiometer with the forward movement of the piercer in the diemouth, the potentiometer controlling the current supply to the pump. Inthis way it should be possible to suppress the oscillation of thepiercer tip entirely. This can be done using any fluid flow controldevice which supplies fluid at a controlled rate to the return thrustsurface of the piercer piston during the forward travel of the ram withthe ram punch and the piercer piston. If the supply of fluid is correctthe piercer tip remains stationary in the mouth of the die.

I claim:

I. A rod and tube extrusion press comprising extrusion die means, a mainextrusion ram adapted to extrude rod or tube through said die means,internal parts of said extrusion ram defining a cylinder therein, apiercer piston within said cylinder, a piercer connected to said piston,hydraulic fluid supply means adapted to supply hydraulic fluid to saidcylinder on one or other side of said piston to advance or retract saidpiercer from said extrusion ram, and means responsive to the axialposition of saidpiercer and controlling said hydraulicfluid supply meanswhereby hydraulic fluid is automatically supplied to said cylinder onsaid other side of said piston to retract said piercer relatively tosaid extrusion ram at a rate to maintain a tip of said piercersubstantially stationary within said die means as said extrusion ramadvances to extrude tube through said die means around said piercer,said axial position responsive means comprising a control element, meansmechanically connecting said control element to said piercer on one sidethereof whereby said control element moves axially with said piercer,and a complementary element adapted to co-operate with said controlelement to control said hydraulic fluid supply means, said controlelement being positioned, when said piercer tip is in'its fullyretracted position, at a distance from said complementary element equalto the distance between said fully retracted piercer tip and theposition of said tip when it is in its advanced position in said diemeans, said hydraulic fluid supply means admitting hydraulic fluid underpressure to said other side of said piston when said control elementengages said complementary element, said means interconnecting saidpiercer and said control element including aflexible tension memberwhich emerges laterally from said extrusion ram;

2. A press according to claim 1, wherein the cooperative function ofsaid elements can selectively be rendered inoperative to'enableextrusion of tube with an advancing piercer.

3. In an hydraulic extrusion press of the type including a die throughwhich extrusion iseffected, a ram for extruding material through saiddie, a piercer adapted to coact with said ram and movable relativethereto, and hydraulic means for controlling the position of saidpiercer, the improvement comprising means for sensing the position ofsaid piercer during said extrusion operation, and means responsive tosaid sensing means for automatically continuously controlling saidhydraulic means to maintain said piercer at-a fixed position relative tosaid die during said extrusion.

4. A press according to claim 3 wherein said responsive means comprisevalve means operable to control fluid flow in said hydraulic means, andwherein said sensing means include trigger means mounted for movementsimultaneously with said piercer and driven thereby, said trigger meansbeing operative to actuate said valve means to maintain said piercer ata predetermined position by controlling fluid flow in said hydraulicmeans.

5. A press according to claim 4 wherein said trigger means include acable attached to said piercer and movable simultaneously therewith.

6. A press according to claim 4 wherein said hydraulic means includepiercer piston means defining a pair of opposed hydraulic chambers fordriving said piercer in either of two opposite directions, said valvemeans operating in response to said trigger means to selectively supplyhydraulic fluid to either of said chambers to maintain said piercerfixed relative to said die at a predetermined position.

1. A rod and tube extrusion press comprising extrusion die means, a mainextrusion ram adapted to extrude rod or tube through said die means,internal parts of said extrusion ram defining a cylinder therein, apiercer piston within said cylinder, a piercer connected to said piston,hydraulic fluid supply means adapted to supply hydraulic fluid to saidcylinder on one or other side of said piston to advance or retract saidpiercer from said extrusion ram, and means responsive to the axialposition of said piercer and controlling said hydraulic fluid supplymeans whereby hydraulic fluid is automatically supplied to said cylinderon said other side of said piston to retract said piercer relatively tosaid extrusion ram at a rate to maintain a tip of said piercersubstantially stationary within said die means as said extrusion ramadvances to extrude tube through said die means around said piercer,said axial position responsive means comprising a control element, meansmechanically connecting said control element to said piercer on one sidethereof whereby said control element moves axially with said piercer,and a complementary element adapted to co-operate with said controlelement to control said hydraulic fluid supply means, said controlelement being positioned, when said piercer tip is in its fullyretracted position, at a distance from said complementary element equalto the distance between said fully retracted piercer tip and theposition of said tip when it is in its advanced position in said diemeans, said hydraulic fluid supply means admitting hydraulic fluid underpressure to said other side of said piston when said control elementengages said complementary element, said means interconnecting saidpiercer and said control element including a flexible tension memberwhich emerges laterally from said extrusion ram.
 2. A press according toclaim 1, wherein the co-operative function of said elements canselectively be rendered inoperative to enable extrusion of tube with anadvancing piercer.
 3. In an hydraulic extrusion press of the typeincluding a die through which extrusion is effected, a ram for extrudingmaterial through said die, a piercer adapted to coact with said ram andmovable relative thereto, and hydraulic means for controlling theposition of said piercer, the improvement comprising means for sensingthe position of said piercer during said extrusion operation, and meansresponsive to said sensing means for automatically continuouslycontrolling said hydraulic means to maintain said piercer at a fixedposition relative to said die during said extrusion.
 4. A pressaccording to claim 3 wherein said responsive means comprise valve meansoperable to control fluid flow in said hydraulic means, and wherein saidsensing means include trigger means mounted for movement simultaneouslywith said piercer and driven thereby, said trigger means being operativeto actuate said valve means to maintain said piercer at a predeterminedposition by controlling fluid flow in said hydraulic meaNs.
 5. A pressaccording to claim 4 wherein said trigger means include a cable attachedto said piercer and movable simultaneously therewith.
 6. A pressaccording to claim 4 wherein said hydraulic means include piercer pistonmeans defining a pair of opposed hydraulic chambers for driving saidpiercer in either of two opposite directions, said valve means operatingin response to said trigger means to selectively supply hydraulic fluidto either of said chambers to maintain said piercer fixed relative tosaid die at a predetermined position.